Extend Lua with custom C functions using Clang

note, May 23, 2023 on Mitja Felicijan's blog

Here is a boilerplate for extending Lua with custom C functions. This requires +Clang and Lua 5.1 to be installed. GCC can be used instead of Clang, but the +Makefile will need to be modified.

  • nativefunc.c

    #include <lua.h>
+#include <lauxlib.h>
+
+static int l_mult50(lua_State *L) {
+  double number = luaL_checknumber(L, 1);
+  lua_pushnumber(L, number * 50);
+  return 1;
+}
+
+int luaopen_nativefunc(lua_State *L) {
+  static const struct luaL_Reg nativeFuncLib[] = {{"mult50", l_mult50}, {NULL, NULL}};
+
+  luaL_register(L, "nativelib", nativeFuncLib);
+  return 1;
+}
+

  • main.lua

    require "nativefunc"
+print(nativelib.mult50(50))
+

  • Makefile

    CC       = clang
+CFLAGS   =
+INCLUDES = `pkg-config lua5.1 --cflags-only-I`
+
+all:
+  $(CC) -shared -o nativefunc.so -fPIC nativefunc.c $(CFLAGS) $(INCLUDES)
+
+clean:
+  rm *.so
+